Biomedical electrodes are used with electrocardiograph ("ECG/EKG") instruments to trace and monitor the electric potentials associated with electric currents that transverse the heart in resting diagnostic procedures, in surgical and emergency room procedures, in cardiac and critical care units in ambulatory monitoring, and in stress diagnostic procedures. The electrodes need to accurately detect and transmit electrical signals produced by biomedical events. Generally this need has required use of relatively large (and therefore) expensive electrical conductors. Electrolyte compositions such as conductive adhesives and conductive gels are used to reduce the size of the electrical conductor. These electrodes also need to stay in place with electrical contact between the skin and the electrode. This requirement can be a problem with all biomedical electrodes and is a particular problem in any circumstance where the electrode stays in place for a long period of time and the patient moves or is moved during monitoring.
U.S. Pat. No. 4,524,087 to Engel discloses a grounding plate biomedical electrode wherein the electrical conductor or "plate" is a polyester film coated on one side with a conductive metal. The conductive metal surface of the plate is coated with an electrically conductive pressure-sensitive adhesive. Overlying the polyester film side of the plate and extending outward from its periphery is an adhesive coated backing to secure the electrode to the skin of a patient. The electrode has a connector tab to electrically connect the electrode to a lead wire. An insulating strip is placed transversely to the connector tab on the exposed surface of the conductive adhesive.
A sensing electrode sold under the brand name Littmann.RTM. Diagnostic EKG Electrode (3M Co., St. Paul, Minn.) includes a film of polymeric material coated on one side with tin. A single, continuous layer of an electrically-conductive pressure-sensitive adhesive covers approximately three quarters of the tin surface while one quarter of the tin surface is a strip along one edge and free for attachment to the lead-wire of an electrical sensing device. The electrically-conductive pressure-sensitive adhesive of the Littmann.sup.R sensing electrode, while adequately conducting electrical current, does not always provide sufficient adhesion to the skin over long periods, e.g., days of ECG/EKG monitoring.
U.S. Pat. No. 4,166,465 to Esty discloses a grounding plate biomedical dispersive electrode with a backing dimensioned to be generally rectangular and provided with bifurcated ends or wings which form a generally broad notch or recessed portion between each of the bifurcated ends. Positioned between the two "wings" is a tab to which a lead-wire connector is attached.
EPO Application Ser. No. 84 307 882.5 (published May 22, 1985) discloses a biomedical electrode having a terminal member, a retainer sheet, an ionically conductive layer, and a medical tape. The terminal member has a base with upper and lower surfaces and a post integral with the base for connection to a lead wire of an electromedical instrument. The retainer sheet and medical tape each have an aperture to receive and surround the terminal post. The retainer sheet overlies the terminal base and the medical tape overlays the retainer sheet. The ionically conductive layer contacts the lower surface by the terminal base and extends peripherally beyond the lower surface of the base to contact the retainer sheet. A metal or metallized layer may be included between the retainer sheet and the upper surface of the base and the retainer sheet and the ionically conductive layer. The retainer sheet and metal or metallized layer are shown with the same surface area and shape and aligned when assembled. The ionically conductive layer is shown with a perimeter equal to that of the retainer sheet and metal or metallized layer. It is assembled with its peripheral edges aligned with those of the retainer sheet and metal or metallized layer. The medical tape has a surface area larger than those of the retainer sheet, the metal or metallized layer and the ionically conductive layer. It extends peripherally beyond the ionically conductive layer to aid in securing the electrode to skin.